Inside printed circuit board under pushbutton

ABSTRACT

An improved structure of printed circuit board (PCB) under pushbutton comprises a base layer and an insulation membrane, wherein a plurality of conductive portions and corresponding contact portions are printed on the base layer and the insulation membrane respectively. A plurality of insulation portions is printed on each contact portion along its circumference; and, no glue will be applied on a corridor between every pair of the conductive potions in the base layer and the contact portions in the insulation membrane when c ombining the insulation membrane to the base layer by gluing or direct printing. By this arrangement, an air channel can be reserved for being applicable to various button groups or waterproof membrane PCBs.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the invention

[0002] This invention relates to an improved structure of printed circuit board (PCB) under pushbutton, more particularly, to a PCB, wherein a circuit pattern can be printed on an insulation membrane and a base layer with waterproof function to fit various button groups, and to lessen thickness of a keyboard when being assembled with other key parts.

[0003] 2. Description of the prior art

[0004] A pushbutton or combination keyboard in large or small scale can be found almost everywhere in household electrical appliance, test instruments, computer, etc for easy control operation.

[0005] A membrane printed circuit board (PCB) used in a personal computer or notebook computer is usually composed of an upper and a lower layer membrane and an insulation layer inserted therein. As there is no glue applied among those three layers, hence, a contact point in the upper and the lower layer membrane respectively will contact each other when a rubber body of pushbutton is pressed down to squeeze air. However, in case a water drop is happened to go into a pushbutton, no sooner has the rubber body restored from the previous state of being pressed than moisture is sucked to intrude upon the inside membrane PCB under pushbutton that is liable to incur a short-circuit problem. Further, in assembling a keyboard, the mentioned PCB is commonly laid firstly on the base layer made of a metallic material before anchoring other button components that inevitably increases thickness, weight, and cost of the keyboard.

[0006] Another kind of PCB contains an upper and a lower flexible layer membrane, wherein a plurality of conductive portions is printed on the upper layer membrane while a plurality of contact portions corresponding with above conductive portions is printed on the lower layer membrane; and, an insulation portion is printed on each contact portion. The upper and the lower layer membrane are glued to form a membrane PCB of this kind.

[0007] Such a membrane PCB is also waterproof all right, nevertheless, it's laid on a metallic base layer before anchoring other button components that inevitably increases thickness, weight, and cost of the keyboard as mentioned above.

SUMMARY OF THE INVENTION

[0008] The primary object of this invention is to eliminate abovesaid defects by printing a circuit pattern on an insulation membrane and a base layer directly to fit various button groups with waterproof function and reduce thickness of the keyboard and production cost after assembling with other button components.

[0009] Another object of this invention is to provide an insulation portion of a PCB circularly and radially disposed around a contact portion of an insulation membrane, or circularly disposed in geometrical shapes, such as circle, square, etc.

[0010] A further object of this invention is to transfer an insulation portion on an insulation membrane to a base layer, so that, it requires printing a contact portion and a circuit pattern only when fabricating the insulation membrane.

[0011] As to realize abovesaid objects, the PCB of this invention comprises a base layer and an insulation membrane, wherein a plurality of conductive portions and corresponding contact portions are printed on the base layer and the insulation membrane respectively; a plurality of insulation portions is printed on each contact portion along its circumference; and, no glue will be applied on a corridor between every pair of the conductive potions in the base layer and the contact portions in the insulation membrane when combining the insulation membrane to the base layer by gluing or direct printing. By this arrangement, an air channel can be reserved for being applicable to various button groups or waterproof membrane PCBs.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] For a better understanding to the present invention, together with further advantages or features thereof, at least one preferred embodiment will be elucidated below with reference to the annexed drawings in which:

[0013]FIG. 1 is a three-dimension elevational view of a PCB of this invention;

[0014]FIG. 2 is a schematic top view of the PCB of this invention;

[0015]FIG. 3 is a vertical sectional view of the PCB of this invention;

[0016]FIG. 4 illustrates action of FIG. 3;

[0017]FIG. 5 is a schematic view of an embodiment of this invention; and

[0018]FIG. 6 is a schematic view of another embodiment of this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0019] As shown in FIG. 1, 2, and 3, an improved structure of inside printed circuit board (PCB) under pushbutton of this invention a waterproof membrane PCB 1 applicable to various button groups comprises a base layer 2 and an insulation membrane 3. The base layer 2 made of a hard plastic material (If a metallic material is adopted, an insulation layer must be printed on its surface to complicate the process.) and the insulation membrane 3 are printed with a plurality of conductive portions 21 and corresponding contact portions 31 respectively. Each contact portion 31 is composed of a pair of contact-sections 311, 312, which is coupled with a signal transmission line 32 individually.

[0020] A plurality of radially arranged insulation portions 33 is circularly printed on the contact portion 31 along its circumference. When the insulation membrane 3 is gluecombined with or printed directly on the base layer 2, a corridor between those two conductive portions 21, 21′ in the base layer 2 and between those two contact portions 31, 31′ in the insulation membrane 3 are reserved free of glue in order to form an air channel 4.

[0021] Please refer to FIG. 3 and 4 a vertical sectional and a schematic action view respectively, wherein a representative rubber body 5 is laid or glued on the insulation membrane 3 of the PCB 1. When the rubber body 5 is pressed down, the contact portion 31, of the insulation membrane 3 is forced to contact with the conductive portion 21 of the base layer 2, and an output signal of pushbutton will be transmitted via the signal transmission line 32 of the contact-section 311, 312. Meanwhile, the air in the space between the conductive portion 21 and the contact portion 31 is squeezed and expelled to a neighboring space formed by another conductive portion 21′ and contact portion 31′ via the air channel 4, so that, moisture infiltration or water drops happened to have been dripped down into a keyboard and sucked to intrude upon the membrane PCB 1 when a rubber body 5 is operated to incur a short-circuit can be prevented.

[0022] As above mentioned, a circuit pattern is printed on an insulation membrane and a base layer directly, thickness, weight, and cost of a completed PCB can be reduced, in addition, a waterproof PCB will ensure durability and a prolonged lifetime of a keyboard made with the structure of this invention.

[0023] As shown in FIG. 5, the foregoing radially arranged insulation portion 33 of the insulation membrane 3 might be formed in other geometrical shapes, such as a circle, a square, etc for being printed on the contact portion 31 along its circumference.

[0024] Another embodiment of this invention shown in FIG. 6 is to transfer the insulation portion 33 of the insulation membrane 3 to the base layer 2, hence, only the contact portions 31, 31′ and the signal transmission lines 32 are required to be printed on the insulation membrane 3.

[0025] Although, this invention has been described in terms of preferred embodiments, it is apparent that numerous variations and modifications may be made without departing from the true spirit and scope thereof, as set forth in the following claims. 

What is claimed is:
 1. An improved structure of inside printed circuit board (PCB) under pushbutton applicable in various button groups, the PCB comprising: a base layer having a plurality of conductive portions disposed thereon; and an insulation membrane being printed or glued on said base layer having a plurality of contact portions disposed thereon corresponding with said conductive portions in positions, wherein a signal transmission line is coupled with each said contact portion, and a plurality of insulation portions is disposed on each said contact portion along its circumference; in virtue of combining said insulation membrane with said base layer by gluing or printing method, a thinner and waterproof PCB being obtainable.
 2. The improved structure of inside PCB under pushbutton according to claim 1, wherein said base layer can be made of a hard plastic material.
 3. The improved structure of inside PCB under pushbutton according to claim 1, wherein said contact portion comprises two contact-sections.
 4. The improved structure of inside PCB under pushbutton according to claim 1, a corridor between each pair of said conductive portions in said base layer and between each pair of said contact portions in said insulation membrane are reserved free of glue when said insulation membrane is glue-combined with said base layer 2 for sustaining an air channel.
 5. The improved structure of inside PCB under pushbutton according to claim 1, wherein said insulation portions can be circularly disposed on each said contact portion in radial manner or in other geometrical shapes, such as a circle, a square, etc.
 6. The improved structure of inside PCB under pushbutton according to claim 1, wherein the insulation portions on said insulation membrane can be transferred to said base layer, hence, only said contact portions and said signal transmission lines are required to be printed on said insulation membrane. 